Injection drug users are at increased risk for injection with mycobacterium and human immunodeficiency virus (HIV). Among patients who have acquired immunodeficiency syndrome(AIDS), Mycobacterium avium complex (MAC) infection is the most common bacterial opportunistic infection. Preliminary data sugguest that active tuberculosis confer protective against MAC infection in patients with AIDS. It has also been suggested that injection drug use nonwhite race confer protection aginnst MAB infection. We hypothesize that latent and active M. Tuberculosis infection confer protective immunity against MAC disease in HIV-infection drug users. We will also determine that protective effect that injection drug use, race and sex confer to the development of MAC disease in HIV-infected persons. To test these hypotheses an observational cohort study will be performed on prospectively collected data from twp cohorts of HIV-infected persons:1) the AIDS Linked to the Intravenous Experience (ALIVE) cohort of injection-drug users and 2) the Johns Hopkins Hospital Adult HIV Clinic cohort.